cron.pl -- Schedule HTTP server maintenance tasks

This module deals with scheduling low frequency maintenance tasks to run at specified time stamps. The jobs are scheduled on the wall clock and thus the interval is kept over server restarts.

 http_schedule_maintenance(+When, :Goal) is det

Schedule running Goal based on maintenance broadcasts. When is one of:

daily(Hour:Min)

Run each day at Hour:Min. Min is rounded to a multitude of 5.

weekly(Day, Hour:Min)

Run at the given Day and Time each week. Day is either a number 1..7 (1 is Monday) or a weekday name or abbreviation.

monthly(DayOfTheMonth, Hour:Min)

Run each month at the given Day (1..31). Note that not all months have all days.

clear

Clear the schedule for the given goal.

This must be used with a timer that broadcasts a maintenance(_,_) message (see broadcast/1). Such a timer is part of library(http/http_unix_daemon).

Arguments:

Goal	- is the goal called. This is executed in the thread that broadcasts the maintenance(_,_) event, i.e., by default in the main thread. If a considerable amount of work is to be done it is adviced to start a detached thread to do the real work.